1. Field of the Invention
The invention is directed to a method for manufacturing a working electrode for an implantable, electrochemical oxygen sensors.
2. Description of the Prior Art
In physiologically controlled heart pacemakers, oxygen concentration in the blood or, tissue often serves as a control parameter for adjusting the pacing rate. An implantable, electrochemical oxygen sensor whose working electrode is a vitreous carbon electrode having a smooth surface has proven advantageous for measuring the oxygen concentration (see European Application 0 170 998). For reducing the oxygen dissolved in the electrolyte, this working electrode is placed for a brief time (about 5-50 ms) at a potential of, for example, -1 V (to Ag/AgCl) and then returns to the quiescent potential (approximately 0 volts). It is an advantage that this working electrode need not be provided with a membrane because the vitreous carbon is electro-catalytically inert for the oxidation of substances present in the electrolyte and only catalyzes the oxygen reduction.
An oxygen sensor of the above type has generally been composed of a two-electrode or three-electrode arrangement, with the electrodes assembled in the form of a catheter. The working electrode (of vitreous carbon) is hemispherically fashioned and forms the tip of the catheter. It would be advantageous, however, if the oxygen sensor could be integrated into the electrode cable of a heart pacemaker. For that purpose, however, the working electrode would have to have an annular shape.